The central premise underlying the San Antonio Nathan Shock Aging Center described in this proposal is that identifying the biological mechanisms underlying aging can best be achieved by studying animal models that show enhanced longevity. Our Center will focus its effort on providing investigators with State-of-the-art scientific infrastructure, resources, services, and unique animal models that are required in studying pertinent questions to the basic biology of aging in mammalian models of enhanced longevity. The Specific Objectives of the San Antonio Nathan Shock Aging Center are as follows: 1. To provide mammalian models of interest to investigators studying aging. The Aging Animal and Longevity Assessment Core will provide investigators with various rodent models of interest to aging, e.g., transgenic/nutritional/pharmacological manipulations, and the Comparative Biology of Aging Core will provide investigators with mammalian species with exceptionally long lifespans. 2. To provide services/resources that will allow investigators to study various molecular and physiological processes believed to play a role in aging in rodents. The Pathology, Oxidative Damage and Mitochondrial Function, Healthspan and Functional Assessment, and Research Development Cores will provide investigators with unique resources/services used to characterize the effect of the various manipulations on aging in whole animals, tissues, or cells. In addition, the Administrative/ Program Enrichment Core will provide investigators with support for data management and statistical analyses. 3. To provide assistance to faculty for developing research programs in aging. The Research Development Core will provide investigators new to aging with pilot grants and mentors to develop research programs in aging that can successfully compete for research grants from federal and private sources. 4. The Administrative/Program Enrichment Core will provide the administrative support necessary to enhance the research environment in San Antonio and to encourage collaborative research on aging among investigators at San Antonio as well as other Nathan Shock Centers and institutions. Over the past 5 years, the San Antonio Nathan Shock Aging Center has provided services to 103 investigators, and 30% of these investigators are from other research institutions.